Aerojet Corporation is a California-based aerospace/defense contractor specializing in missile and space propulsion, and defense and armaments. Aerojet has been or is responsible for the Aerobee rocket (retired in 1985), the Apollo Service Module's main engine, the Titan first- and second-stage liquid-propellant engines (including those on the current Titan IV), the Delta second-stage liquid engine, the Atlas V solid rocket motors, the Space Shuttle orbital maneuvering system, the NEAR-Shoemaker propulsion system, the X-33 reaction control system, the X-38 de-orbit propulsion stage, and the MESSENGER propulsion system. It is also involved in developments with NASA's Second Generation Reusable Launch Vehicle program – a major component of the Agency's Space Launch Initiative.
Aerojet was formed in 1942 as Aerojet Engineering Corp., by Theodore von Kármán; Frank Malina; Martin Summerfield, a Ph.D. candidate at the California Institute of Technology; John W. Parsons, a self-taught chemist; and Ed Forman, a skilled mechanic. In its early years, Aerojet focused on building and developing rocket motors for JATO (Jet-Assisted Take-Off).